(1) Field of the Invention
The present invention is an attenuation meter and method of use for measuring an optical beam in a liquid medium.
(2) Description of the Prior Art
Presently, there are commercially-available meters designed to measure an optical beam attenuation co-efficient “c” in water. The beam attenuation co-efficient equals the natural logarithm of the ratio of the input power to the output power of a single frequency collimated light beam divided by a propagation length. The beam attenuation co-efficient accounts for both absorption and scattering of the light beam.
In order to limit the size of measuring meters; the meters utilize optical propagation paths that are less than one meter in length. In clear water, attenuation lengths (1/attenuation coefficient=1/c) are often greater than eight meters.
The greater, the attenuation length then the greater the effort needed to maintain an acceptable cleanliness on an optical surface. There is also a greater effort needed to maintain the accuracy of measurement electronics and the accuracy of calibration procedures. Because of these real world scenarios, the measurements provided by these meters in clear water are generally non-repeatable and inaccurate to the extent that the measurements are unusable.
As such, there is need for an attenuation meter and method of use that can provide accurate measurements of an optical attenuation coefficient in a liquid medium with comparatively low attenuation rates—such as a clear water environment.